This invention relates to a novel realization of a single ended mixer/up-converter with the performance comparable and exceeding in some characteristics that of a balanced configuration.
The balanced approach has the drawback of requiring two mixer diodes which increases the cost, size and local oscillator power requirements. However, frequently all of these factors are overlooked because the balanced arrangement has an inherent advantage of local oscillator noise cancellation. Another viable approach to noise reduction and utilization of one mixer diode is filtering, i.e., introducing a filter in the local oscillator branch of the mixer with appropriate preselection. This approach, in the past, has not been very attractive since the local oscillator power requirement is considerably greater than for the balanced arrangement. The power requirement is greater because of losses due to filter and coupler, where the coupler (usually at least 10 db) is used for local oscillator to RF isolation. This will be discussed further in conjunction with FIG. 1.